Electronic flash tube apparatus



May 10,1949. R. B. BASHAM 2,469,913

ELECTRONIC FLASH TUBE APPARATUS Filed Feb. 15, 1947 2/ g /9 Ill"; X"

RAYMOND. B. BASHAM INVENTOR.

Patented May 10, 1949 UNITED STATES TENT OFFICE Raymond B. Basham, Fort Worth, Tex., assignor to Westronics, Inc., Fort Worth, Tex., a corporation of Texas Application February 15, 1947, Serial No. 728,912

1 Claim.

This invention relates to photographic equipment, and has reference to repeating electronic flash tube apparatus.

An object of th invention is to provide improvements in apparatus of the referred to class whereby higher efiiciency is attained, and wherein there is less drain on the battery of the device.

Another object of the invention is to provide, in a flash tube apparatus, higher voltage stability, i. e., to provide means whereby the voltage delivered at the flash tube will not vary.

Another object of the invention is to provide means in apparatus of the referred to class whereby the flash tube cannot be operated unless the delivered voltage is high enough to produce suflicient light output and thus prevent underexposure of the film.

A further object of the invention is to provide a. light-weight and small power pack unit for operating flash tubes attached to cameras.

These and other objects will become apparent from the accompanying drawing, wherein:

Figure 1 is a wiring diagram of an exemplary form of the invention, and

Figure 2 is a wiring diagram of an electronic synchronizer which may be used in conjunction with flash tube apparatus, such as illustrated in Figure 1.

The numeral I designates a source of power such as a battery or the like. The negative terminal of the battery is connected with a vibrator reed 2 which is preferably short and stiff to produce a high peak wave form.

The reed 2 is positioned for operation with a vibrator transformer 4 and the vibrator point 5 of which is connected with the primary of the said transformer and, in turn, is connected with a condenser 6 between the said primary and the vibrator reed connection 3. A power switch I is connected between the positive terminal of the battery I and the primary of the transformer 4.

The secondary of the transformer 4 is connected with the anode of a rectifier 8, whereas the other end of the said secondary is connected with the cathode 9 of the flash tube II! to be operated by means of a connecting wire I I. Another condenser I2 stores energy for discharging the flash tube III and is connected in parallel between the cathode of the rectifier 8 and the secondary connecting wire I I. Similarly, a gas filled discharge tube I3 and resistor I4, connected in series with respect to each other, are also connected in parallel with the said secondary wire I I and cathode of the rectifier 8, the said discharge tube and resistor together forming a voltage regulator.

The cathode of the rectifier 8 is connected with the anode of the flash tube It by means of a connecting wire it. Another wire i'i is connected between the discharge tube I3 and resistor I4 and is connected with the primary of an ignition coil i 8 after passing through a momentary trip switch I9. A condenser 28 is connected in parallel between the wire IB and the induction coil lead i'I, preferably near the resistor I4 for compactness.

Both the primary and secondary of the ignition coil I8 are connected with the wire it at corresponding ends, whereas the remaining end of the ignition secondary is connected with the igniter electrode 2| of the flash tube It.

By closing the power switch I, the transformer 4 is energized and its magnetic field excites the reed 2. The reed 2 is normally in contact with the vibrator point 5. The condenser 6 tunes the transformer 4 to the natural frequency of the vibrator reed 2. By reason of the described short stiff reed, the frequency of the vibrator is set to produce a high peak wave form in the transformer secondary. Since this peak is of a uni-directional polarity, it makes possible a low inverse voltage when used with a half -wave rectifier. The high peak wave thus formed is regulated by the discharge tube I3 and resistor I4. The electrodes of the discharge tube I3 are so spaced that the said tube does not start to discharge until the desired voltage is reached. The resistor I4 is adjusted to draw enough current through the discharge tube It to maintain an equilibrium with the source of power I. The condenser 20 across the resistor I4 charges up to the voltage drop that appears across the said resistor when the discharge tube I3 conducts. By closing the momentary trip switch I9, the condenser 20 is discharged, and thus energizes the flash tube II].

It is to be understood that the momentary trip switch I 9 is connected for coaction with the shutter of a camera (not shown).

The novel electronic synchronizer, illustrated in Figure 2, may be connected in the wire I! between the trip switch I9 and the condenser 20. The tube illustrated is a cold cathode thyratron and is generally referred to by the numeral 22, and is herein referred to as a trigger tube. The control grid of the tube 22 is connected with the anode of the same through a variable resistor 23. Similarly, the control grid is connected with the cathode of the tube 22 through a resistor 24 which has a condenser 25 connected across the last referred to resistor 24. A keep-alive current limiting resistor 23 is connected in series between the anode and the cathode of the tube 22.

When the trip switch I9 is closed, the anode of the trigger tube 22 will be immediately made positive with respect to the cathode. The condenser 25 then starts to charge, making the control grid of the tube 22 go from zero voltage to some positive voltage approaching that of the anode. The gas in the tube 22 will then break down and the tube will conduct. The condenser 20, previously referred to, is then discharged into the primary of the ignition coil l8, and causing the flash tube It to be energized. The time delay of the synchronizer 22 may be regulated by the variable resistor 23.

What I claim is:

A flash tube unit comprising: a grid controlled flash tube, a high voltage direct current supply including positive and negative terminals, a positive lead connecting said positive terminal with the anode of said flash tube, a negative lead connecting said negative terminal with the cathode of said flash tube, an ignition coil includin primary and secondary windings, said secondary winding bein connected between the grid and the anode of said flash tube, a condenser connected between said primary and said negative leads, a voltage regulator comprising a gas filled discharge tube and resistor connected with each other in series and between said positive and said negative leads, and an ignition coil lead connected between said discharge tube and said resistor of said voltage regulator and with one end of said primary Winding of said ignition coil, means connecting the remaining end of said primary winding of said ignition coil with the anode of said flash tube, a condenser connected between said positive lead and said ignition coil lead, and a switch within said ignition coil lead between said primary winding and the last said condenser.

RAYMOND B. BASHAM.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date Re. 22,611 Edgerton Mar. 6, 1945 1,917,418 Almquist et al July 11, 1933 2,113,762 James Apr. 12, 1938 2,274,365 Gardiner Feb. 24, 1942 2,290,264 Wuerfel July 21, 1942 2,341,541 Grier Feb. 15, 1944 2,383,492 Klemperer Aug. 28, 1945 

